Impeller and mixer-settler apparatus

ABSTRACT

A variable ratio impeller apparatus in which vanes extend through perforations in a baffle which is movable to vary the proportion of the vanes extending on either side of the baffle permits adjusting the ratio of mixing action to pumping action produced by the impeller. In a mixer-settler liquid-liquid contact apparatus, the impeller apparatus is substantially vertically positioned in a mixing vessel with the vanes extending over and spaced not more than 0.05 times the diameter of their sweep from proximately located plural inlets communicating with the bottom of the mixing vessel. Means are provided for transferring liquid from the mixing vessel to a settling vessel provided with a baffle to minimize turbulance produced by the liquid transfer.

United States Patent Primary ExaminerRobert W. Jenkins Attorneys-Richard W. Sternberg, Roger R. Jones and Thomas N. Wallin ABSTRACT: A variable ratio impeller apparatus in which vanes extend through perforations in a baffle which is movable to vary the proportion of the vanes extending on either side of the baffle permits adjusting the ratio of mixing action to pumping action produced by the impeller. In a mixer-settler liquid-liquid contact apparatus, the impeller apparatus is substantially vertically positioned in a mixing vessel with the vanes extending over and spaced not more than 0.05 times the diameter of their sweep from proximately located plural inlets communicating with the bottom of the mixing vessel. Means are provided for transferring liquid from the mixing vessel to a settling vessel provided with a baffle to minimize turbulance produced by the liquid transfer.

[72] inventors Walter M. Davis Beverly, Mass.; Edwin A. Matzner, St. Louis, Mo. [21] Appl. No. 752,231 [22] Filed Aug. 13, 1968 [45] Patented Feb. 2, 1971 [73] Assignee Monsanto Company St. Louis, Mo. a corporation of Delaware [54] IMPELLER AND MIXER-SETTLER APPARATUS 4 Claims, 3 Drawing Figs.

[52] US. Cl 259/23 [51] lnt.Cl B01f 7/16 [50] Field of Search 259/66, 23, 8, 7, 2, 24, 43,44, 67; 230/1 14; 103/97 [56] References Cited UNITED STATES PATENTS 2,845,936 8/1958 Boynton 259/66 g I 2' i IMPELLER AND MIXER-SETTLER APPARATUS BACKGROUND OF THE INVENTION This invention relates to an impeller apparatus which simultaneously provides pumping and mixing action and is adjustable so as to vary the ratio of mixing action to pumping action. The invention further relates to a liquid-liquid contact apparatus of the mixer-settler type. Impellers which simultaneously provide both pumping and mixing action are known to the art. In many operations in which such impellers are utilized, the ratio of pumping to mixing action is critical. For example, in solvent extraction procedures and washing operations wherein substantially immiscible liquids are pumped into a mixer, mixed and thereafter separated, the rate at which the liquids are pumped into the mixing chamber relative to the mixing action is often critical. If the pumping action is disproportionately greater than the mixing action, the liquids will be ineffectively mixed so as to render the extraction or washing operation inefficient. Conversely, if the liquids are overly mixed, power is wasted in the mixing operation and in some cases the liquids may emulsify so as to defy separation.

Since, in hitherto known impellers, the ratio of pumping to mixing action is fixed, such impeller must be designed and fabricated for the specific conditions of intended use. Changes in process conditions, such as desired flow rate, liquids, or liquid ratios, necessitate fabrication of specially designed impellers suited for use in the changed process.

SUMMARY OF THE INVENTION It is an object of this invention to provide a variable ratio impeller apparatus having both pumping and mixing action wherein the ratio of the pumping action to the mixing action is readily adjustable.

A further object of the invention is to provide a mixer-settler apparatus which facilitates proper mixing of substantially immiscible liquid components followed by the rapid separation of these components.

Basically, these and other objects are accomplished, in accordance with this invention, by an impeller having vanes extending through a perforated baffle which is adjustable to vary the portion of the vanes extending on either side of the baffle and by a mixer-settler apparatus utilizing such impeller.

The invention will be better understood by reference to the drawings and the description of the preferred embodiments.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective front elevation of an impeller apparatus illustrating one embodiment of this invention. FIG. 2 is a perspective front elevation, partially in section, of an impeller apparatus illustrating another embodiment of this invention. FIG. 3 is a front elevation in cross section of a mixersettler apparatus of this invention.

[DESCRIPT ION OF THE PREFERRED EMBODIMENTS One embodiment of the impeller apparatus of this invention is described by reference to FIG. 1. As shown, vanes are attached to a shaft 11 which is provided with means (not shown) for effecting rotation thereof about a vertical axis. The vanes extend through perforations in a baffle 12. Means for adjusting the relative positions of the baffle l2 and vanes 10 with respect to each other are provided by rods 13 connecting the baffle to collar 14. The baffle can be adjusted to vary the portion of the vanes extending on either side thereof and the set screw 15 provides means for Securing the baffle in fixed position relative to the vanes. Pumping action is increased and mixing action decreased by moving the baffle in the direction shown by the arrow. Movement of the battle in the opposite direction increases mixing action and decreases pumping action. Both pumping and mixing action can be increased by increasing the speed of rotation of the impeller or decreased by decreasing the speed of rotation. Thus, by varying the speed of rotation and the position of the baffle, the desired degree of pumping and mixing action is readily obtained.

If it is inconvenient or uneconomical to provide means for varying rate of impeller rotation, an embodiment such as shown in FIG. 2 may be advantageously employed. As shown, a second baffle 12a is provided which is adjustable independently of baffle 12. Baffle 12a is provided with a leaf 16 fitted with a set screw 15a which can be tightened to secure baffle 12a in fixed position. Since the area of the vanes between the baffles provides no pumping and relatively little mixing action, this embodiment of the invention permits independent adjustment of pumping and mixing action.

The mixer-settler apparatus of this invention will be understood by reference to FIG. 3. As shown, this apparatus comprises a mixing vessel 17 and a settling vessel 18. Means for transferring fluid from the mixing vessel to the settling vessel is provided by the lowered lip 19 of the common wall between these vessels.

Proximately located inlets in the form of concentric conduits 20 and 21 communicate with the bottom of mixing vessel 17. An impeller apparatus as previously described is substantially vertically positioned in mixing vessel 17 so that the vanes 10 extend over the inlets 20 and 21. The vanes are spaced from the inlets by a distance less than 0.05 times the diameter of the sweep of the vanes. If spaced a greater distance, pumping action is very inefficient. In operation, liquids are pumped from the inlets, mixed, and transferred by the pumping action of the impeller from mixing vessel 17 over lowered lip 19 to the settling vessel 18. A baffle 22 is disposed in the settling vessel to minimize the turbulance produced in the settling vessel by the transfer of liquid thereto. The optimum baffle position for use with various flow conditions can be determined from well-understood hydrodynamic principles and routine tests. Preferably, the baffle also defines a channel for introduction of liquid into the settling vessel at an optimum level.

It is known that separation of admixed immiscible liquids is sometimes facilitated by maintaining constant temperatures to minimize interference with settling caused by thermal circulation. Therefore, it is often desirable to maintain adiabatic conditions by surrounding a portion of the mixer settler apparatus with insulation means 23 in which heating means such as resistance heating wire 24 are'disposed. The settling vessel is provided with means (not shown) for exiting or withdrawing either or both fractions of the separated liquids.

Although this invention has been described by reference to specific embodiments, various modifications and functional equivalents within the scope of the appended claims will be apparent to those skilled in the art.

We claim: 1

l. A mixer-settler apparatus comprising in combination:

a. a mixing vessel;

b. a settling vessel;

c. means for transfer of fluid from said mixing vessel to said settling vessel;

d. at least 2 proximately located inlets communicating with the bottom of said mixing vessel;

e. a variable ratio impeller apparatus comprising a perforated baffle, vanes extending through the perforations in said baffle, means for adjusting the relative position of said baffle and said vanes with respect to each other to vary the portion of said extending on either side of said baffie, and means for securing said baffle and said vanes in fixed position relative to each other, said apparatus being substantially vertically positioned in said mixing vessel, the vanes of said impeller apparatus extending over said inlets and being spaced therefrom by a distance less than 0.05 times the diameter of the sweep of said vanes;

f. a baffle disposed in said settling vessel to minimize the tur-, bulence produced in said settling vessel by transfer thereto of fluid from said mixing vessel; and

g. means for withdrawing liquid from said settling vessel.

2. The apparatus of claim 1 wherein said inlets are concentric conduits.

3. The apparatus of claim 2 wherein said baffle in said settling vessel defines a channel therein.

4. The apparatus of claim I further comprising insulation .means having heating means disposed therein at least partially surrounding said vessels. 

1. A mixer-settler apparatus comprising in combination: a. a mixing vessel; b. a settling vessel; c. means for transfer of fluid from said mixing vessel to said settling vessel; d. at least 2 proximately located inlets communicating with the bottom of said mixing vessel; e. a variable ratio impeller apparatus comprising a perforated baffle, vanes extending through the perforations in said baffle, means for adjusting the relative position of said baffle and said vanes with respect to each other to vary the portion of said extending on either side of said baffle, and means for securing said baffle and said vanes in fixed position relative to each other, said apparatus being substantially vertically positioned in said mixing vessel, the vanes of said impeller apparatus extending over said inlets and being spaced therefrom by a distance less than 0.05 times the diameter of the sweep of said vanes; f. a baffle disposed in said settling vessel to minimize the turbulence produced in said settling vessel by transfer thereto of fluid from said mixing vessel; and g. means for withdrawing liquid from said settling vessel.
 2. The apparatus of claim 1 wherein said inlets are concentric conduits.
 3. The apparatus of claim 2 wherein said baffle in said settling vessel defines a channel therein.
 4. The apparatus of claim 1 further comprising insulation means having heating means disposed therein at least partially surrounding said vessels. 